Global model runs discussion

[DESTRUCTION5]

Im not sold on any of the development part but any rain of any kind would be nice...

[wxman57]

I think it's focusing on a weak upper-level low in the region the first week of May. Sort of what the Canadian model does with every upper-level low.

[Tampa Bay Hurricane]

IF El Nino does decide to develop this summer, there would
be a better chance of a June tropical storm. 1997 had several
early season storms. The subtropical jet comes
off the Pacific and tends to bring fronts to the gulf coast
and Florida that are more unstable. Hybrid development
in mid-May from a low that comes out of the caribbean and
becomes subtropical (like 2007 TS Barry) with a front/trough
in the NE gulf? This is just a wild guess (based partly
on a subtropical El Nino Pattern). But anything to put out
the drought/fires! Barry in 2007 dumped several inches on my hungry
grass.

[cycloneye]

There is anything yet from the EURO about what GFS has been showing for the past few days about a system forming in the SW Caribbean.Until other models chim in and show glimmers of something,I will continue to be unconvinced that what GFS is showing may come to fructition.

http://www.ecmwf.int/products/forecasts ... 7091412!!/

[Ivanhater]

18z GFS..
develops it in about 8 days

[gatorcane]

The GFS wants to develop a low from an area of disturbed weather that forms South of Panama in the EPAC as early as 5 days from now. A couple of surface Highs that currently dominate most of the Atlantic Basin shift farther East and merge as a cold front from the CONUS dives SE.

By day 7 the powerful ridge that is over the Western Caribbean, FL, and the Bahamas has weakened leaving a large weakness from the SW Caribbean all the way northward into the SE CONUS. That causes this low to jump over to the SW Caribbean and gather strength as upper-level winds die off considerably.

Then from day 10-13 the GFS only slowly moves this low Northward while it gains strength. That is because some ridging develops behind the first short-wave blocking its progress and even inducing a WNW to NW movement for some time. Another short-wave extending from a large Vortex moving ENE through the Great lakes, drags a cold front Southward creating another weakness. This weakness then shoots this system off to the NNE then NE through the West Coast of Florida in this run.

It's all a long way off -- but I'm betting a large area of disturbed weather does develop south of Panama and starts to creep northward in the SW Carib. Look for that by the end of this week and into the weekend. What happens after that is up to debate. I'm still looking for UKMET and ECMWF support especially.

Right now I'm thinking some moisture starts to gather in the Western Carib for early next week, and hopefully rain chains for Southern Florida do increase as the moisture gets dragged northward in front of the second short wave. As Wxman mentioned, it could even be an upper-level low feature the GFS is wanting to develop. Either way it would bring some much needed rainfall to Florida.

[gatorcane]

Seems the GFS wants to bring this thing anywhere from as far West as the Yucatan and Eastern GOM and as far East as Eastern Cuba and the Bahamas:

00Z GFS run is through South Florida in two weeks:



06Z GFS run is through Eastern Cuba in two weeks:

[KWT]

The key now is whether or not the GFS keeps the timeframe moving forward, for these things thats usually the acid test.

[gatorcane]

12Z NAM just out is showing a broad area of low pressure and disturbed weather just south of Panama in the EPAC and extending into the SW Carib. This is 84 hours from now. This is what the GFS has been showing for several runs now. Other models such as CMC and NOGAPS also show a broad area of lower pressures in this area so models are agreeing that some lower pressures are going to develop in this area.

You can be assured that this area of disturbed weather will create alot of broken convection in this area. What is not certain is if it will organize into something of significance (i.e. a depression, TS, or something more). Once we start seeing alot of convection in the SW Caribbean which I think we will, I will bet some interest will rise from members. Now, its hard for them to believe anything will happen given the stable conditions there. But the key is not what is happening now but what could happen later.

Note that High pressure dominating most of the Western Atlantic and Carib is starting to exit off to the East that will leave alot of low pressure way down in the SW Carib.

[gatorcane]

12Z GFS has an organized system now as early as 7 days in the SW Carib. By Day 8, it has deepened further as shown in the image below. The GFS consistency can no longer be dismissed and the fact we are talking the 7 day range is increasing the chances of something getting going in the SW Carib. Question is, will it be an upper-level low or a low-level tropical entity?

[cycloneye]

Question is, will it be an upper-level low or a low-level tropical entity?

The big question is if other models will follow GFS.Oh yeah! now it goes over me,in other words its all over the place.

[gatorcane]

Cycloneye in the latest run heads for Puerto Rico. Each run is farther east it seems.

[Ivanhater]

Well I'm not to interested in the path this far out, that will obviously change many times. I am just shocked the GFS is still showing this every run. Forms in about 7 days..amazing

[HURRICANELONNY]

I just hope it rains soon. My grass needs it bad.

[AJC3]

For those so inclined to follow this thread, you'll probably want to keep tabs on the discussion from the HPC tropical desk over the next several days...

http://www.hpc.ncep.noaa.gov/discussions/fxca20.html

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
145 PM EDT TUE APR 28 2009

DISCUSSION FROM APR 28/0000 UTC. AT MID LEVELS...THE MODELS
INITIALIZE A RIDGE OVER CENTRAL/NORTHERN MEXICO... ORIGINATING ON
A HIGH NORTH OF JALISCO. THE RIDGE PATTERN GRADUALLY WEAKENS
THROUGH 60-72 HRS...AS SHORT WAVE PERTURBATIONS STREAM ACROSS THE
SOUTHWEST USA/NORTHERN MEXICO. MEANWHILE...THE RIDGE ALOFT IS
FEEDING COLD POLAR ENERGY INTO AN ELONGATED TROUGH OVER THE
CENTRAL GULF/ SOUTHERN MEXICO. THIS TROUGH PERSISTS THROUGH 72
HRS...AND IT IS TO ENHANCE DIURNAL CONVECTION FROM PUEBLA/OAXACA
TO CHIAPAS IN SOUTHERN MEXICO...AS WELL AS ACROSS PORTIONS OF
GUATEMALA-HONDURAS/NORTHERN EL SALVADOR. IN THIS AREA WE PROJECT
RAINFALL AMOUNTS OF 10-15MM/DAY AND MAXIMA OF 30-60MM.

AT 250 HPA IT REFLECTS AS A SHORT WAVE TROUGH FROM OAXACA IN
SOUTHERN MEXICO TO THE PACIFIC ALONG 100W TO 00N. THIS TROUGH...A
TUTT...PERSISTS THROUGH 72-84 HRS. THE TUTT IS INTERACTING WITH
THE PACIFIC ITCZ AS THE LATTER MEANDERS ALONG 07N/08N INTO
COLOMBIA. AS CONVECTION BECOMES MORE ACTIVE...THE MODELS
CONSISTENTLY SHOW A SURGE IN MOISTURE ACROSS PANAMA-COSTA RICA TO
THE CENTRAL CARIBBEAN. AS A RESULT...WE PROJECT A GRADUAL INCREASE
IN CONVECTION FROM WESTERN PANAMA TO COSTA RICA/SOUTHERN
NICARAGUA. ON DAY 01 EXPECT RAINFALL ACCUMULATION OF 10-15MM/DAY
AND MAXIMA OF 20-40MM. ON DAYS 02 AND 03 THE MAXIMA WILL INCREASE
TO 30-60MM. OVER NORTHEAST HONDURAS/NICARAGUA THE MAXIMA WILL PEAK
AT 15-30MM/DAY.

OVER NORTHERN SOUTH AMERICA THE DOMINANT FEATURE ALOFT IS THE
SUBEQUATORIAL RIDGE...WITH AXIS AT 250 HPA EXTENDING ACROSS THE
GUIANAS-VENEZUELA/COLOMBIA ALONG 05N. THROUGH 72 HRS THE RIDGE
BECOMES BETTER ORGANIZED WHILE ANCHORING ON A HIGH OVER/NORTH OF
THE GUIANAS. AT MID LEVELS...A NARROW RIDGE EXTENDS ACROSS THE
TROPICAL ATLANTIC ALONG 10N INTO VENEZUELA/COLOMBIA. UNDER
INFLUENCE OF A TROUGH TO THE NORTH...THE RIDGE OVER WESTERN
VENEZUELA/COLOMBIA WEAKENS THROUGH 60-72 HRS...WHILE PERSISTING
OVER THE GUIANAS/ EASTERN VENEZUELA. THE PERSISTENCE OF THIS RIDGE
ALOFT... AND THE TUTT OVER THE EASTERN PACIFIC...IS TO ALSO INCITE
A SURGE IN ITCZ RELATED CONVECTION OVER WESTERN-NORTHERN PORTIONS
OF COLOMBIA. FURTHERMORE...THE CLIMATOLOGICAL/ PANAMANIAN
LOW-TROUGH BECOMES BETTER ORGANIZED THROUGH 36-48 HRS...AND
PERSISTS THROUGH 72-84 HRS WITH ANCHORING LOWS MIGRATING TO THE
WEST JUST SOUTH OF PANAMA. FURTHERMORE... THE MJO IS TRENDING
TOWARDS MORE FAVORABLE CONDITIONS (DIVERGENT ALOFT) ACROSS THE
REGION...AND LONG RANGE FORECAST MODELS SHOW THIS CONDITIONS
PERSISTING FOR A COUPLE OF WEEKS. CONVECTION ON THE CAUCA
VALLEY-EJE CAFETERO TO THE DARIEN IN PANAMA/GULF OF URABA WILL
INCREASE FROM 20-40MM/DAY EARLY THIS PERIOD TO 40-80MM/DAY BY DAY
02-03. LOCALLY HIGHER AMOUNTS ARE QUITE POSSIBLE. OVER NORTHERN
COLOMBIA TO SANTANDERES AND NORTHWEST VENEZUELA WE EXPECT MAXIMA
OF 15-30MM ON DAY 01...TO INCREASE TO 30-60MM/DAY ON DAY 03.
LOCALLY HIGHER AMOUNTS ARE ALSO POSSIBLE.

SOUTHERN COLOMBIA-VENEZUELA ARE UNDER INFLUENCE OF THE ITCZ...AND
DIURNAL CONVECTION IN THIS AREA WILL FAVOR MAXIMA OF 20-40MM/DAY
THROUGH 48-60 HRS. BUT ACTIVITY IS TO GRADUALLY BECOME MORE ACTIVE
BY 72-84 HRS...WHEN MAXIMA IS TO PEAK AT 30-60MM/DAY. OVER THE
GUIANAS...AS THE MID LEVEL RIDGE PATTERN DOMINATES...CONVECTION
WILL BE MORE SPARSE AND WILL DEPEND ON SEA BREEZE EFFECT DURING
THE DIURNAL HEAT CYCLE...TO RESULT IN RAINFALL AMOUNTS OF
00-05MM/DAY AND MAXIMA TO GENERALLY RANGE BETWEEN 10-20MM.
SLIGHTLY HIGHER AMOUNTS ARE POSSIBLE ON DAY 03...WITH MAXIMA OF
15-25MM.

OVER THE WESTERN ATLANTIC...AT MID/UPPER LEVELS...THE MODELS
INITIALIZE A SPLIT FLOW PATTERN...WITH A RIDGE DOMINATING THE
NORTHERN STREAM FLOW AND A TROUGH THE SOUTHERN STREAM. THIS IS A
SLOW TO EVOLVE PATTERN...WITH THE 500 HPA TROUGH TO MEANDER OVER
THE BAHAMAS/NORTH OF THE GREATER ANTILLES THROUGH AT LEAST 60 HRS.
BY 72-84 HRS THE TROUGH IS TO START ITS EASTWARD MIGRATION AS THE
PATTERN OVER NORTH AMERICA EVOLVES. MEANWHILE...CYCLONIC VORTICES
WILL ROTATE AROUND THE BASE OF THE TROUGH...AND THEY ARE TO
PROPAGATE FROM EASTERN CUBA TO THE NORTHERN LEEWARD ISLANDS. THESE
WILL PROVIDE THE TRIGGER FOR PERIODS OF DEEP CONVECTION OVER THE
NORTHERN CARIBBEAN ISLANDS. AT 250 HPA A SUBTROPICAL JET MAXIMA
BOUNDS THE SOUTHERN PERIPHERY OF THIS TROUGH...AND IT WILL REMAIN
NORTH OF PUERTO RICO/ HISPANIOLA THROUGH AT LEAST 60-66 HRS.
OBJECTIVE ANALYSIS SHOWS ALTERNATE PERIODS OF
CONVERGENCE/DIVERGENCE ALOFT UNDER INFLUENCE OF THIS
JET/PERSISTENT TROUGH PATTERN. AT LOW LEVELS A WANING RIDGE OVER
THE WESTERN ATLANTIC GRADUALLY PULLS TO THE NORTH AND EAST. THE
ASSOCIATED PRESSURE GRADIENT OVER THE BASIN GRADUALLY
SLACKENS...WHICH RESULTS IN DECREASE IN TRADE WIND EASTERLIES
ACROSS THE CARIBBEAN. EARLY IN THE PERIOD THE WINDS WILL PEAK AT
20-30KT...BUT BY THE END OF THIS CYCLE THEY WILL DECREASE TO
10-15KT.

THE TROUGH NORTH OF THE ISLANDS IS INDUCING A SERIES OF INVERTED
TROUGHS IN THE LOW/MID LEVEL EASTERLIES...THAT THEN PROPAGATE WEST
ACROSS THE BASIN AS THEY EMBED IN THE PREVAILING TRADES. THE
AMPLITUDE OF THESE WAVES RANGE BETWEEN 05-10 DEGREES...AND THEY
TEND TO BE SHORT LIVE... DISSIPATING OVER THE CENTRAL/WESTERN
CARIBBEAN. BUT FROM EASTERN CUBA/JAMAICA TO PUERTO RICO AND THE
LEEWARD ISLANDS THEY FAVOR AN ACTIVE PATTERN. ACROSS
CENTRAL/EASTERN CUBA TO THE SOUTHEAST BAHAMAS/THE TURKS IT WILL
FAVOR RAINFALL AMOUNTS OF 00-05MM/DAY AND MAXIMA OF
10-15MM...WHILE OVER JAMAICA WE EXPECT ACCUMULATION OF 10-15MM/DAY
AND MAXIMA OF 25-50MM THROUGH 36-48 HRS...AND 15-25MM/DAY BY 72-84
HRS. OVER HISPANIOLA TO PUERTO RICO THE MAXIMA WILL RANGE BETWEEN
25-50MM ON DAY 01...AND AS HIGH AS 30-60MM ON DAY 02...WITH A
SLIGHT DECREASE ON DAY 03. OVER THE LEEWARD AND FRENCH ISLANDS
EXPECT MAXIMA OF 15-25MM ON DAY 01...TO DECREASE TO 10-15MM ON
DAYS 02 AND 03. AN INCREASE IS POSSIBLE OVER THE SOUTHERN WINDWARD
ISLANDS AND THE ORINOCO DELTA REGION IN NORTHEAST VENEZUELA ON DAY
03...WITH MAXIMA OF 15-25MM.

ALVARADO...ETESA (PANAMA)
GONZALEZ...IDEAM (COLOMBIA)
DAVISON...NCEP (USA)

[gatorcane]

Thanks AJC3, I'll monitor those discussions.

The 12Z ECMWF shows absolutely nothing at 240 hours -- GFS still pretty much alone on this system.

Since the ECMWF is not on board the doubt is there.

BTW - moisture on the increase across Panama, the EPAC, and SW Carib -- expect this to further become more disturbed with broken convection areas as the week progresses as the whole area gradually lifts northward and potentially consolidates more in the SW Carib.

[HURAKAN]

The first week of May.

[cycloneye]

Accuweather gets into the mix about this.

http://www.accuweather.com/mt-news-blog ... or_tro.asp

[KWT]

Very unusual to get a storm in early May as that picture shows, though the far SW Caribbean is a good place for May development. Wonder if we could get an invest from this, if nothing else at all.

[Evil Jeremy]

Even if this does not form, I think this is would be a good time for the NHC to run one of their test invests that they do every year or so. Still waiting for more model agreement on this though.